1. Field of the Invention
The invention relates to a fuel injection system for internal combustion engines and having a high-pressure pump supplied with fuel from a low-pressure source.
2. Description of the Prior Art
The field of use of the inventionxe2x80x94unlike fuel injection systems of the distributor typexe2x80x94is unit fuel injector injection systems (so-called UISs) and pump-line-nozzle injection systems (so-called UPSs). In such injection systems, in the region of the magnet valve seat, because of the fuel inlet conduit and outlet conduits discharging there, or in other words because of the greatly reduced liquid pressure in these conduits, cavitation erosion can occur. The (unwanted) consequence can be a shortened service life of the affected UIS or UPS injector.
The object of the invention is to avoid cavitation erosion in the region of the magnet valve seat.
Because of the reduction in cross section of the fuel inlet and outlet bores effected by graduation in the direction of the low-pressure valve chamber, a slight throttling of the fuel flow in these conduits is attained. The consequence is a corresponding increase in pressure, which reduces or entirely prevents the development of cavitation bubbles. The later implosion of cavitation bubbles could cause cavitation erosion damage at the valve seat (needle and/or body) in the low-pressure valve chamber or in the fuel inlet and outlet bores. Such damage is thus avoided by the cross-sectional reductions, graduated according to the invention, in the applicable conduits.